The present invention relates generally to nail driving devices and more particularly to a pneumatic nail driving machine for automatically fastening of pallets, boxes and the like.
Automatic or semi-automatic nailers are well known and typically are either portable, hand-held devices or larger, stationary machines which perform repetitive nailing operations. Of this latter type, to which our present invention pertains, it has heretofore been common to mount the machine in an upright manner such that the nailing operation is carried out solely in a vertical, downward direction. This vertical arrangement of known, stationary, nailing machines, of course, simplifies the feeding of nails thereto in that nails can be delivered to the machine merely by the force of gravity. While this gravity nail delivery method is, indeed, simple, it nevertheless, imposes an operational limitation upon the machine in that the machine is operable only in a vertical, downward direction. As a result, if the object being nailed, such as a pallet, requires nailing on opposite sides, it is necessary to first nail the top and then turn the pallet over in order to nail the bottom. This proves to be a time consuming and costly operation.
In an effort to solve this problem, it has been recognized that the nails could be collated into strips, held by clips or the like, and fed directly to the nailer, without the aid of gravity. A nail strip of this type is shown in U.S. Pat. No. 4,253,598. While this mode of nail transfer yields greater freedom in respect of nailing direction, it, likewise, increases the cost of the manufacturing operation as a result of the added expense of collated nails.
Attempts have also been made to feed individual nails, pneumatically, through a tube to hand-held nailers, as disclosed in U.S. Pat. Nos. 3,049,713 and 2,879,509. These prior devices deliver the nails directly into a cylindrical passageway adjacent to the driving ram. They generally utilize mechanically awkward, nail delivery systems having a number of moving parts which are prone to jam or malfunction during use.
It is also known to utilize magnets in nail driving devices as a means to hold and position a nail prior to being driven, as disclosed in U.S. Pat. Nos. 4,049,181, 2,829,369 and 4,049,181. These drivers utilize gravity fed nail systems which also possess the inherent vertical alignment shortcommings of the aforementioned devices.
In addition to the nail feeding and alignment problems heretofore encountered with known nailing machines, the problem of over-driving or wood splitting is a re-occurring problem due to the fact that the common driving ram is cylindrical in shape and tends to press into the wood after the nail has been driven. This is particularly true when the wood being assembled is of varying hardness or contains an excess amount of knots. In these situations, the nailing machine is usually set to drive a nail into an area having the greatest hardness. Unfortunately, when a nail is driven into a soft area, the cylindrical driver, under this highr impact setting, either indents the surface of the wood, drives the nail through the outer surface or splits the wood, thus causing a poor appearance or a scrap piece.
It has also been recognized that a fast acting, nail-driving piston is desirable in order to set the nail in a timely, economic manner. In this regard, air actuated, pneumatic pistons have been used in a variety of ways so as to effect a quick extension and retraction thereof. Generally, these devices employ a plurality of nested cylinders having various exhaust and inlet air ports machined therein in an effort to accomplish this end. Exemplary of such devices are the nail drivers shown in U.S. Pat. Nos. 3,049,713, 2,993,208 and 2,989,750. It is readily apparent that these cylinders add to the cost of the device due to the required machining, material and assembly expenses.
Our present invention solves many of the problems heretofore found in these prior devices by providing an automatic nailing machine which utilizes a supply of loose nails and is operable in any nailing direction i.e., vertical, horizontal, inverted or any other desired position therebetween.
The nailing machine of the present invention further provides a pneumatic device which delivers nails to the driving chamber of the machine in a fast and trouble-free manner with a minimum amount of moving parts so as to decrease the probability of jamming, expensive down-time and needless maintenance.
Our present invention still further provides an automatic nailing machine having a single, air actuated cylinder with air exhaust means associated therewith to permit instantaneous extension and retraction of the nail driving piston therewithin. In addition, our invention provides a nail driving machine which drives the nail to a uniform depth without splitting the wood.
The nail driving machine of the present invention achieves these desirable features by providing a transfer tube which feeds loose nails, by pressurized air, at high velocity, to an inclined X-shaped alignment chamber which is positioned adjacent to a sidewall of the guide channel of the pneumatic ram. A magnet is positioned along an opposed sidewall of the guide channel to attract the inclined nail and place the nail in an aligned position within the guide channel of the driving ram. The pneumatically driven ram is rectangular in cross-section and carries a slightly extended, nail seating tip, which engages the head of the nail and countersinks the nail to a depth equivalent to the length of the seating tip. The larger, rectangular surface area of the ram, surrounding the seating tip, strikes the surface of the wood and acts as a stop, preventing further extension of the ram, thus preventing any damage to the wood. Our invention further provides a rotatable sleeve having exhaust ports formed therein positioned on the base of the driver cylinder. When the ram piston is moved through a work or extension cycle, the sleeve automatically rotates to a closed position upon completion of the work cycle to permit a rapid, pressurized retraction of the ram piston. Air is rapidly exhausted from the cylinder during the retraction cycle by a poppet valve positioned on the cylinder head plate.